The present invention relates generally to an apparatus for automatically shutting off fluid flow in a fluid conduit under predetermined conditions and more specifically to an improved flow control device for stopping fluid flow through a conduit when either a predetermined flow quantity or a predetermined time interval is exceeded.
Many types of automatic beverage dispensing devices, particularly those in commercial establishments or workplace employee kitchens, are supplied with water by a permanent branch plumbing line which interconnects the dispensing device with a local or municipal pressurized water supply system. A single branch plumbing line may supply water to one or more dispensing devices, including such appliances as coffee brewers, drink dispensers and ice makers, which are often located in close proximity to one another. Costly damage can occur in buildings if a malfunction in a dispensing device, or a break in the branch water line supplying the device, occurs at a time when the building or kitchen area is unattended or unoccupied. In particular, a malfunction or break which results in the free flow of water from a branch plumbing line will produce serious damage in a multi-story building, if allowed to run for many hours or over a weekend.
Various kinds of flood protection systems have been developed to deal with the threat of floods caused by leaking pipes. Such prior art systems include systems which incorporate specialized circuitry to detect pressure drops caused by a burst pipe, as in U.S. Pat. No. 4,735,231; timers which shut off a valve under certain conditions in the event of a long leak, also shown in U.S. Pat. No. 4,735,231; or sensors positioned at low points in the building or plumbing system to detect the presence of leakage water, as in U.S. Pat. No. 4,705,060. One disadvantage of prior art flood protection systems is that most systems are activated to shut off the flow in the branch plumbing line based on the time that flow continues, or on more complicated time-and-pressure or time-and-flow rate conditions. An example of the latter is found in U.S. Pat. No. 4,881,948. However, time of flow is not the most relevant factor in determining whether a continuous flow of fluid through a conduit is in fact creating a damaging or potentially damaging flood. If, for example, a branch water line supplying a beverage dispenser experiences reduced water pressure, the dispensing device may require additional time to fill a dispensing reservoir. Should that time exceed the pre-set maximum allowable time interval for a time-based flood protector, the protector will automatically shut off the plumbing line when no flood or leakage condition actually exists. Systems which detect the presence of leakage water at low points to determine if a flood is occurring, such as in U.S. Pat. No. 4,705,060, have the obvious disadvantage of being difficult to install due to multiple sensors at separate locations and the fact that considerable damage may already have occurred by the time the flood is detected.
Although prior art flood protection devices, such as those described above, do function to help control leaks which continue for an excessive time period or which produce sufficient flooding to trigger remote sensors, a better approach would be to incorporate a flood protector on a branch plumbing line which measures the actual flow quantity of fluid flowing in the line and which shuts off the line when an excessive flow quantity is detected.
Automatic fluid-flow control devices are also used for other purposes. Various kinds of dispensers employ automatic flow controllers to produce a brief, measured flow of fluid during a single dispensing cycle. An example of a beverage dispenser which employs such a flow controller is an automatic coffee brewer. In most coffee brewers, a tank with heating elements heats the water to the proper brewing temperature. Fresh water is admitted to the tank, usually by a solenoid valve which is controlled by a timer, each time the tank is refilled. Most flow controllers in such applications open the valve for a predetermined time interval and then reclose it, completing a single dispensing cycle. The disadvantage of using a flow controller which cuts off the flow after a predetermined time interval is that the actual quantity of water admitted to the tank can vary as the water pressure changes. It would be preferable to have a fluid-flow controller for controlling flow in a fluid conduit which admits only a predetermined quantity of fluid through the conduit during one dispensing cycle, rather than opening the conduit for a predetermined time interval.
An improved automatic fluid-flow control system would offer protection against excessive fluid flow, such as during a leak condition, but would not prematurely cut-off fluid-consuming devices before a flood actually develops. It would be particularly advantageous to have an automatic fluid-flow control system which permits only a predetermined quantity of fluid to pass through a branch conduit. It would also be advantageous to have an automatic fluid-flow control system which includes a back-up, redundant, protective shut-off which can engage the protective function even if the primary, flow quantity-based, shut-off fails. It would also be advantageous to have an improved automatic fluid-flow control system which can, using the same circuitry, perform either a flood protection function on a branch pluming line or serve as a automatic flow controller for use in a beverage dispenser or the like, allowing for economies of scale in manufacturing the flow controller to reduce the cost of both types of automatic flow controllers.
Accordingly, a fluid-flow control system is provided for shutting off the flow in a conduit under selected conditions by means of a signal-controlled valve. The system, in operative condition, comprises a flow monitor operatively connected to such a conduit for providing a first signal containing information about the volume of fluid flow in the conduit. The system also includes signal analyzing circuitry operatively connected to the flow monitor and the valve for analyzing the first signal to distinguish periods of substantial fluid flow from periods of no-flow in the conduit. The signal analyzing circuitry also measures the approximate quantity of fluid passing through the conduit during each period of substantial fluid flow. And the signal analyzing circuitry also closes the valve when a predetermined quantity of fluid passing through the conduit is exceeded.
In its preferred form, the signal analyzing circuitry of the fluid-flow control system includes a signal detector to establish the start and end of each period of fluid flow in the conduit. The signal detector outputs a reset signal to initialize the flow quantity measuring device during each period of no-flow. As such, the flow quantity measuring device is ready to begin accumulating a quantity measurement at the start of each period of substantial fluid flow. A secondary, back-up shut-off circuit is also preferably included in the control system to measure the time interval during each period of interrupted fluid-flow. The timer closes the valve when a predetermined interval is exceeded. The predetermined time interval is selected to exceed the longest anticipated interval required for the predetermined flow quantity to pass through the conduit. As such, the timer will only operate to close the valve when a malfunction has occurred in the primary protective circuitry.